In the field of the silver halide photograhic materials, especially those intended for camera use, recently, photographic materials of ultra-high sensitivity have become widely used, and ISO 1600-color negative film is a typical example. In order to enhance the sensitivity of photographic materials, it has heretofore been propelled to enlarge the size of the silver halide grains contained in said materials, which, however, results in deterioration of the graininess of said grains. In conventional films of ISO 100 and 400, the size thereof has recently been required to be a small format one, and therefore it is requested to make the graininess of the silver halide grains used in said films further better.
It is generally known that a monodispersion emulsion having a uniform grain size distribution is superior to a polydispersion emulsion in that the graininess in the toe region of the characteristic curve thereof is especially excellent. Among said monodispersion emulsions, in particular, normal crystalline grains can be controlled during the formation step of the grains or during the chemical sensitization step thereof, without any remarkable variation of the grain (e.g., variation of the grain size, variation of the form, variation of the sensibility, etc.) and thereby can obtain excellent graininess. Accordingly, said normal crystalline grains bring a great merit in order to enhance the sensitivity in this industrial field. These are described in T. H. James, The Theory of the Photographic Process, Fourth Edition, Chapter 21, The Macmillan, 1977.